1. Field of the Invention
The present invention relates to an ink jet apparatus, and more particularly to an ink jet recording apparatus with which recording is carried out by discharging ink from a recording head onto a recording medium. The present invention also relates to a method for recovery of an ink jet apparatus, and more particularly to a method for recovery of an ink jet recording apparatus.
2. Related Background Art
A recording apparatus records images (the term "images" herein includes characters) according to image information (the term "image information" herein includes character information or the like) on a recording medium such as paper, a thin plastic film, textiles or any other medium capable of having an image recorded thereon. Such a recording apparatus can function as a printing machine, a copying machine, a facsimile machine and so on, or as an output terminal of a composite electronic machine, such as a work station or the like, functioning as a computer, a word processor and so on. Such a recording apparatus can be characterized by its recording method as an ink jet apparatus, a wire dot apparatus, a thermal printing apparatus, a laser beam apparatus and so on.
In a serial-type recording apparatus using a serial scanning method, in which main scanning is carried out in a main scan direction transverse to a sub-scan direction of conveyance of a recording medium, the recording of images is carried out by a recording means carried on a carriage which moves in the main scan direction along a recording medium after the recording medium is positioned at a predetermined recording region. After recording of one line is finished, a predetermined amount of conveyance of the recording medium in the sub-scan direction is carried out. Then recording of the next line on the stationary recording member is carried out. The main scanning and the sub-scanning are repeated alternately. In this way, recording on the whole recording medium is carried out.
On the other hand, in a line-type recording apparatus, in which the only movement is the sub-scanning of a recording medium, recording of one line is carried out at almost the same time the recording member is positioned at a predetermined recording region. Then a predetermined amount of conveyance of the recording medium (a pitch of one line) is carried out and recording of the next line is carried out at almost the same time. The one-line recording and the sub-scanning are repeated alternately. In this way, recording of the whole recording medium is carried out.
Among the foregoing recording apparatuses, an ink jet recording apparatus carries out recording by discharging ink from a recording head to a recording medium. An ink jet recording apparatus has many advantages. It is relatively easy to make the recording means compact. Images with a high density can be recorded rapidly. Recording on plain paper can be carried out without special treatment of the paper. The running cost is relatively low. Recording can be carried out quietly because it uses non-impact method. In addition, it is easy to carry out color recording by using a plurality of color inks. Especially, a line-type ink jet recording apparatus with a type full-line type recording means which has a plurality of discharge openings extending over the width of a recording area of a paper can carry out recording rapidly.
Particularly, an ink jet recording head utilizing thermal energy to discharge ink can be made very compact. One of the reasons for the compact design resides in the manufacturing method used to make the head. That is, a typical ink jet recording head with a high density of liquid paths (or discharge openings) can be manufactured easily by providing members for forming walls of liquid paths, a top plate and so forth on a heater board member with electro-thermal converting bodies through semiconductor manufacturing processes such as etching, deposition, sputtering or the like.
FIG. 1 is a schematic vertical cross sectional view showing an ink discharging portion of an ink jet recording head 90. As illustrated in FIG. 1, a plurality of discharge openings 10 are provided at a certain pitch in a substantially vertical direction on a surface of a recording head 90, which is positioned opposed to a recording medium 1, such as recording paper, which leaves a certain gap (for example, about 0.5 to 2.0 mm) from the surface. A heat generating portion 11 of an electro-thermal converting body for generating thermal energy to be utilized to discharge ink is provided on a wall of each liquid path 10A which communicates between a common liquid chamber 10B and each discharge opening 10. The ink jet recording head 90 is carried on a carriage (which is not shown in FIG. 1) so that the discharge openings 10 are disposed in line transverse to the direction of the movement of the carriage (the main scanning direction). Ink is discharged as a droplet 12 from a selected discharge opening 10 of the recording head 90 by driving the corresponding electro-thermal converting body according to a discharge signal to generate a bubble 11A by film boiling of the ink in the corresponding liquid path 10A. Referring to FIG. 1, heat drivers 13 to be turned on and off are provided corresponding to each of the discharge openings 10 of the recording head 90 to provide discharge signals to each of the electro-thermal converting bodies. A circuit board of a driving circuit to drive the heat drivers 13 is carried, for example, on the carriage.
FIG. 2 is a schematic perspective view showing a main portion of a color ink jet recording apparatus of a serial scanning type with a recovery means for carrying out a recovery treatment of recovering or preventing clogging of a discharge opening of an ink jet recording head and the resulting deterioration of an ink discharge condition from the discharge opening. As illustrated in FIG. 2, a recording head 511Y for discharging yellow color ink (Y), a recording head 511M for discharging magenta color ink (M), a recording head 511C for discharging cyan color ink (C), and a recording head 511K for discharging black ink (Bk) are carried on a carriage 512, which is supported along a guide rail 513 to move in a reciprocating manner. A recording medium 514 is conveyed in a sub-scanning direction transverse to a main scanning direction of a movement of the carriage 512 and the recording heads 511 through a recording area, which is in a range of the movement of the carriage 512. In the recording area, a predetermined gap (a flying distance of a droplet, for example 0.5 to 1.5 mm) is provided between a front surface (a surface on which discharge openings are provided) of the recording heads 511 and a recording surface of the recording medium 514.
The movement of the carriage 512 is carried out through a timing belt 521 by driving a carriage motor (a main scanning motor) 520 in either direction. Conveyance of the recording medium 514 from a tray 522 is carried out by conveying rollers 515, 516. Maintaining a position of the recording medium 514 in the recording area is carried out by guiding and supporting a reverse side of the recording medium 514 on a platen 525.
The multiple color recording of one line onto the recording medium 514 is carried out by discharging ink from selected discharge openings in the order of Y, M, C and Bk in response to image signals in synchronism with the movement (main scanning) of the recording heads 511 while the recording medium 514, which is disposed in the recording area, is suspended. Timings of discharging each color ink are controlled by the output from a control circuit, which is not illustrated in FIG. 2, according to signals which are read by an encoder 517. After recording of the one line, the conveyance (sub-scanning) of the recording medium 514 for one line is carried out. Then the recording of the next line is carried out again as the recording heads 511 move (main scanning). The main scanning and the sub-scanning are repeated alternately. In this way, desired images are printed on the recording medium 514. Numerals 523a, 523b designate ink reservoirs which contain ink to be supplied through an ink tube member 524 to the respective ink jet recording heads 511.
A recovery apparatus for maintaining and recovering a discharge capability of the recording heads 511 is generally situated at a predetermined position, for example a home position of the carriage 512, which is in the range of the movement of the carriage 512 but out of the recording area. This recovery apparatus has cap members 508 for covering and closing tightly discharge openings of each recording head from the atmosphere, a cleaning wiper member 519 for wiping off extraneous matter like viscous ink on the surface of the discharge openings of each recording head, and a suction pump (which is not illustrated in FIG. 2) connected to the cap members 508 for carrying out the suction recovery by exerting a suction force on the discharge openings when they are covered by the cap members 508.
The cap members 508 are generally made of non-gas-permeable elastic and prevent clogging of the discharge openings by extraneous matter such as viscous ink or dust. For example, in case recording is not carried out for a certain time in an ink jet recording apparatus, the cap members 508 cap the recording heads.
The cleaning wiper member 519 is generally made of a plate-shaped elastic body such as urethane rubber and can be moved back and forth with a holder 518 of the cleaning wiper member 519 by a driving means which is not illustrated in FIG. 2. In case wiping of the surface of the discharge openings is necessary, the cleaning wiper member 519 is moved forward by the driving means and the surface of the discharge openings makes contact with the cleaning wiper member 519 by utilizing the movement of the carriage 512.
In addition, another recovery treatment involving idle ink discharges (pre-discharges) can be performed at the home position by discharging ink (for example, into the cap members 508) according to discharge signals.
In an ink jet recording apparatus, when a power source of the apparatus is turned on, recovery control (warming-up control), which includes the foregoing recovery processes, is carried out to ensure the head is in condition for making a recording of high quality.
Whether the discharge openings are covered by the cap members or not when the power source is turned on depends in most apparatuses whether they were covered when the apparatus was last turned off. If the power source was turned off before capping was carried out, for example by power failure, there is a possibility that the discharge openings have been left uncapped for a long time.
Warming-up recovery control according to the related background art has encountered some drawbacks. When the power source is turned on, previous approaches assumed that the discharge openings were capped, regardless of the actual situation. Therefore, for example, if the power source of the ink jet recording apparatus was turned off before the discharge openings were capped, and the discharge openings have thus been left without being capped for a long time, the usual warming-up recovery control may not be able to maintain the desired level of recording quality because the viscosity of ink is increased. In other words, there is a possibility that ink will not be discharged and recording will not be carried out when the ink jet recording apparatus is operated.
On the other hand, it would not solve the problem to assume that the discharge openings were not capped regardless of the actual situation. That would involve always performing recovery processes when the apparatus is turned on, thus unnecessarily using ink and spending time if the discharge openings had been capped when the apparatus was turned off.
In addition, some ink jet recording apparatuses include a control sequence in which the discharge openings are capped automatically when the power source is turned off. However, in that case the control circuitry becomes more complicated and therefore increases the apparatus cost and the automatic sequence may not work if the power supply is interrupted by something other than turning off the power swatch.